1. Field of the Invention
The present invention relates to prevention of smudging of ink on a recording sheet in a recording apparatus, such as an inkjet recording apparatus.
2. Description of the Related Art
Technologies for inkjet recording apparatuses have been proposed that prevent smudging of ink on a surface of a recording sheet due to contact between the recording sheet and a recording head surface. Japanese Patent Laid-Open No. 2003-39758 describes a technology that prevents rising of a recording sheet and contact between the recording sheet and a recording head surface by attracting the recording sheet toward a platen by using an air suction mechanism. However, it is difficult to mount the air suction mechanism in an inkjet recording apparatus because the air suction mechanism would increase the size and the cost of the inkjet recording apparatus, which is usually small and inexpensive.
Japanese Patent No. 2994392 describes a recording apparatus in which a contact point between a conveying roller and a pinch roller, which are disposed upstream of a recording head, is located above a surface of the platen, and the pinch roller is disposed so as to be offset toward the platen from the top of the conveying roller. Thus, the recording sheet is conveyed in a direction such that the recording sheet is pressed against the platen, whereby rising of the recording sheet above the platen is suppressed and smudging of ink on a surface of the recording sheet due to contact between the recording sheet and the recording head surface is prevented. Because a specific component for preventing rising of the sheet is not used, this structure is suitable for an inkjet recording apparatus in terms of size and cost.
In the recording apparatus described in Japanese Patent No. 2994392, at the moment when the trailing end of a recording sheet P passes a contact point between the conveying roller and the pinch roller (hereinafter referred to as a conveying roller nip), the trailing end of the recording sheet P is placed on the conveying roller in the vicinity of the top of the conveying roller, which is higher than the platen.
In order to reduce printing time, a carriage motor is usually decelerated right after discharging of ink has been finished, so that a carriage 17 (see FIGS. 3A to 3C), which supports a recording head and which is scanning a recording sheet P, is temporarily stopped, and then scanning in the opposite direction is immediately started. Therefore, even when printing is performed up to a side edge of the recording sheet P in the width direction, the carriage 17 is stopped at a position at which a part of the carriage 17 faces the side edge of the recording sheet. If printing is finished at a position that is separated from the side edge of the recording sheet P by a certain distance, the recording head surface may be stopped above the recording sheet P. In general, a recording head protector, which is a member independent from or integrated with the carriage 17, is disposed on the carriage 17 so as to have a height the same as that of the recording head surface. The recording sheet P rises above the upper surface of the platen 14 as illustrated in FIG. 3B at the moment when the trailing end of the recording sheet P passes the conveying roller nip in a state in which the recording head surface and the recording head protector are stopped above the recording sheet P. As a result, the recording sheet P contacts the recording head surface and the recording head protector. Because ink mist adheres to the recording head surface and the recording head protector, ink smudges are transferred to the surface of the recording sheet P that contacts these members. This phenomenon more frequently occurs when the outer diameter of a conveying roller 8 is large, the length of the ink discharge nozzle array is large, and the distance between the conveying roller nip and an upstream eject roller 22 is large. Therefore, the surface of the recording sheet P contacts the recording head surface and a part of the carriage surrounding the recording head surface, and ink smudges adhere to the recording sheet P.